1. Field of the Invention
The invention relates to a method for the manufacture of a micromodule with flush connectors.
A micromodule is the miniature unit formed chiefly by one or more integrated circuit chips and a connector formed by substantially plane and thin regions made of metal. It is designed to be inserted into an information carrier of small thickness such as a chip card or memory key so that the connector is flush with the surface of the information carrier, the chip being embedded in the carrier.
This connector enables the connection to external systems with which the chip of the micromodule will exchange information elements.
International standards define the different characteristics of the micromodule and its connector (these are the ISO 7810 to 7816 standards).
2. Discussion of the Related Art
There are various known methods used to manufacture micromodules. A particular problem of manufacture lies in the coating of the chip with resin in order to protect it from chemical pollution and mechanical stresses. Indeed, the external surface of the connector, namely the surface used for the physical connection of the micromodule to an external system should not be polluted. Whatever the prior art method, a dielectric material is used with the grid that supports the regions of the connector. This dielectric material is molded or cut out so that it covers the interstices between the different regions so as to prevent the resin from flowing over the external face of the regions of the connector. This results in lengthy and costly manufacturing methods. In particular, for the making of micromodules in tape form, using a method for the bonding of a perforated dielectric tape on a pre-slotted metal grid, it is necessary to use a dielectric material having high thermal expansion with respect to the metal grid so as there is no offset. It is also necessary to choose a dielectric that can be used in a small thickness in view of the fact that it is necessary to have small thickness for the micromodules. Finally, it is necessary to have instruments enabling high precision to cut out the tape and adjust it very precisely to the grid. These methods of manufacture are not at all standard as compared with methods used to manufacture integrated circuits.
Now, for certain applications, it is necessary to be able to manufacture micromodules in large batches at a very low cost. In particular, these are disposable prepaid chip cards (as distinct from rechargeable chip cards) and especially phone cards.